Particulate solids are used in a variety of applications including chemical processing and steam generation. For example, particulate solids are widely used to accomplish hydrocarbon cracking and heat transfer. In many applications, the particulate solids are heated to a very high temperature, typically above 1500.degree. F., and are caused to move through the system at high flow rates.
In the past, problems have been encountered in regulating the flow of particulate solids. Specifically, the high temperatures and high flow rates of the solids adversely affect the performance and life of mechahical valves. Consequently, various non-mechanical flow control means have been developed to appropriately regulate the flow of particulate solids.
U.S. patent application Ser. No. 342,393, filed Jan. 25, 1982 discloses a recently developed system that operates without moving mechanical parts to regulate the flow of particulate solids. The system described therein is well adapted to a high mass flow, high temperature environment, and effectively functions as a non-mechanical valve. More specifically, the non-mechanical valve described in application Ser. No. 342,393 includes a standpipe located intermediate an upstream source of particulate solids and a downstream passage into which the particulate solids pass. The standpipe functions as a seal between the pressure at the upstream and downstream locations. The downstream end of the standpipe is configured to accommodate a slumped mass of particulate solids at its lowest point. A source of pressurized fluid communicates with a plenum chamber connected to the standpipe immediately upstream from the slumped mass.
In operation, the standpipe is always filled with particulate solids from the upstream source. Pressurized fluid imposes a pressure on the slumped mass of particulate solids to cause the particulate solids from the slumped mass to move downstream and into the downstream passage.
The rate of flow of particulate solids into the downstream passage varies directly with the magnitude of the pressure differential between the respective upstream and downstream sides of the slumped mass. Therefore, the rate of flow of particulate solids into the downstream passage can be varied by changing the pressure from the source of pressurized fluid. To change the pressure a mechanical valve can be provided intermediate the source of pressurized fluid and the plenum chamber. Appropriate adjustments to the valve then can be made to affect the rate of flow of particulate solids into the downstream passage. Alternatively, in application Ser. No. 342,393 it is shown that in certain applications a sensing line can extend from the pressure source to the steam lines in the associated furnace. The pressure then can be varied as a function of the steam conditions.